If somebody isn't up for the rigours of coursework in their discipline, can they pursue a Masters degree just for creative research contributions? I am on these antipsychotics that affect my focus and intelligence, but I have lots of research.
You would have to find a university willing to go along and I think that would be pretty rare. Most MS degrees include at least some coursework, though some might let you design a program. I'll guess that a small, rather than a large, program would be more willing to let you design a personalized program, though it would take some convincing.
But the bigger issue is that you also need an advisor who you need to convince that you have the required background and knowledge to do research and to do it ethically and correctly. The grades in your coursework give some indication of that.
Also related, though maybe less important is that the university in granting your degree has to put its "stamp of approval" on you and say to the world that you are qualified. That may be harder to do without coursework.
But it is the knowledge and background that are important, not the courses per se that matter.